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From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, pbonzini@redhat.com, alex.bennee@linaro.org
Subject: [PATCH 3/3] softmmu: Remove cpu_reloading_memory_map as unused
Date: Sat, 26 Aug 2023 16:24:15 -0700	[thread overview]
Message-ID: <20230826232415.80233-4-richard.henderson@linaro.org> (raw)
In-Reply-To: <20230826232415.80233-1-richard.henderson@linaro.org>

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-common.h   |  1 -
 accel/tcg/cpu-exec-common.c | 30 ------------------------------
 2 files changed, 31 deletions(-)

diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 87dc9a752c..41788c0bdd 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -133,7 +133,6 @@ static inline void cpu_physical_memory_write(hwaddr addr,
 {
     cpu_physical_memory_rw(addr, (void *)buf, len, true);
 }
-void cpu_reloading_memory_map(void);
 void *cpu_physical_memory_map(hwaddr addr,
                               hwaddr *plen,
                               bool is_write);
diff --git a/accel/tcg/cpu-exec-common.c b/accel/tcg/cpu-exec-common.c
index 9a5fabf625..7e35d7f4b5 100644
--- a/accel/tcg/cpu-exec-common.c
+++ b/accel/tcg/cpu-exec-common.c
@@ -33,36 +33,6 @@ void cpu_loop_exit_noexc(CPUState *cpu)
     cpu_loop_exit(cpu);
 }
 
-#if defined(CONFIG_SOFTMMU)
-void cpu_reloading_memory_map(void)
-{
-    if (qemu_in_vcpu_thread() && current_cpu->running) {
-        /* The guest can in theory prolong the RCU critical section as long
-         * as it feels like. The major problem with this is that because it
-         * can do multiple reconfigurations of the memory map within the
-         * critical section, we could potentially accumulate an unbounded
-         * collection of memory data structures awaiting reclamation.
-         *
-         * Because the only thing we're currently protecting with RCU is the
-         * memory data structures, it's sufficient to break the critical section
-         * in this callback, which we know will get called every time the
-         * memory map is rearranged.
-         *
-         * (If we add anything else in the system that uses RCU to protect
-         * its data structures, we will need to implement some other mechanism
-         * to force TCG CPUs to exit the critical section, at which point this
-         * part of this callback might become unnecessary.)
-         *
-         * This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which
-         * only protects cpu->as->dispatch. Since we know our caller is about
-         * to reload it, it's safe to split the critical section.
-         */
-        rcu_read_unlock();
-        rcu_read_lock();
-    }
-}
-#endif
-
 void cpu_loop_exit(CPUState *cpu)
 {
     /* Undo the setting in cpu_tb_exec.  */
-- 
2.34.1



  parent reply	other threads:[~2023-08-26 23:25 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-26 23:24 [PATCH 0/3] softmmu: Use async_run_on_cpu in tcg_commit Richard Henderson
2023-08-26 23:24 ` [PATCH 1/3] softmmu: Assert data in bounds in iotlb_to_section Richard Henderson
2023-08-27  9:39   ` Alex Bennée
2023-08-26 23:24 ` [PATCH 2/3] softmmu: Use async_run_on_cpu in tcg_commit Richard Henderson
2023-08-27  9:58   ` Alex Bennée
2023-08-27 14:54   ` Richard Henderson
2023-08-27 20:17     ` Alex Bennée
2023-08-27 21:16       ` Richard Henderson
2023-08-29 10:50   ` Jonathan Cameron via
2023-08-26 23:24 ` Richard Henderson [this message]
2023-08-27  9:59   ` [PATCH 3/3] softmmu: Remove cpu_reloading_memory_map as unused Alex Bennée

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